1. Field of the Invention
The present invention relates to a chalcogenide glass, and more specifically to a chalcogenide glass of AgTlS.sub.2 suitable for use in infrared optical devices.
2. The Prior Art
Various attempts have been made to produce broad band infrared transmissive chalcogenide glasses but only arsenic trisulfide (As.sub.2 S.sub.3) has proved suitable for commercial applications. See, for example, J. A. Savage and S. Nielsen, Infrared Physics 5, 195, (1965); and A. R. Hilton, C. E. Jones, and M. Brau, Infrared Physics 4, 213 (1964). Since the IR transmission range of the oxide glasses is very much limited by the metal-oxide structural vibrations, attempts have been made to improve the physical and chemical properties of IR glasses by employing compositions that contain selenium, tellurium and sulfur. Selenide and telluride glasses containing Tl, Sb and Cu have been studied but have very low softening temperatures and low transmittance. See, The Structures of Glass, Vol. 2, Proceedings of the Third all Union Conference on Glassy State, Leningrad 1959.
Increasing demands for IR glasses for a variety of applications including infrared windows, laser beam selectors, laser beam deflectors and fiber-optic transmission lines indicate a need to provide a glass capable of transmitting up to the longer wavelengths, such as 1-5 and 8-14 .mu.m atmospheric windows.
In spite of these disclosures, there remains a need for a economical chalcogenide glass which transmits beyond 12 .mu.m and which provides superior illumination, ranging and handling in the 1-5 and 8-14 .mu.m atmospheric windows.